The present invention relates to an internal combustion engine which comprises an operation angle adjustment mechanism for continuously varying an operation angle of intake valves, and more particularly to an engine control system which easily and accurately corrects the operation angle of the intake valves.
Japanese Patent Provisional Publication No. 2000-234533 discloses a control system for continuously varying an operation angle (a valve opening duration) of intake valves of an internal combustion engine and for continuously varying an opening phase of the intake valves relative to a crank angle.
However, if such a control system is employed in an internal combustion engine having a plurality of cylinder trains such as a V-type internal combustion engine, it is necessary to strictly equalize initial operational properties of intake valves between the cylinder trains so as to prevent degradations of an engine operational stability and an energy consumption. Such an accurate initial setting of the engine requires difficult and complicated procedures.
It is therefore an object of the present invention to provide a control system of an engine control system which improves an engine performance by accurately correcting an operation angle of intake valves without complicating the control system.
Another object of the present invention is to provide an internal combustion engine which improves an engine operational stability and an energy consumption by eliminating a variation between operation angles of a plurality of cylinder trains.
A further another object of the present invention is to provide an improved internal combustion engine which certainly prevents interference between a piston and intake valves during a correcting operation of an operation angle of the intake valves.
An aspect of the present invention resides in a control system of an internal combustion engine which comprises an operation angle adjustment mechanism which continuously varies an operation angle of intake valves of the engine, an air-fuel ratio detector which is disposed in an exhaust passage of the engine and detects an exhaust parameter indicative of air-fuel ratio information, and a control unit which is coupled to the operation angle adjustment mechanism and the air-fuel ratio detector. The control unit is programmed to feedback-control an air-fuel ratio of the engine on the basis of the exhaust parameter and to correct the operation angle on the basis of the exhaust parameter.
Another aspect of the present invention resides in a method for controlling an internal combustion engine with an operation-angle adjustment mechanism for continuously varying an operation angle of an intake valve and an air-fuel ratio detector for detecting an exhaust parameter indicative of air-fuel ratio information. The method comprises a step of feedback-controlling an air-fuel ratio of the engine on the basis of the exhaust parameter; and a step of correcting the operation angle on the basis of the exhaust parameter.
The other objects and features of this invention will become understood from the following description with reference to the accompanying drawings.